The long-range goal of this research is to understand the processes involved in the evolution and dissemination of bacterial antibiotic resistance plasmids. Substantial evidence now exists to indicate that antibiotic producing organisms such as Streptomyces may be the source of at least some of the antibiotic resistance genes that have spread among populations of pathogenic bacteria. The proposed research is a multifaceted effort to elucidate mechanisms involved in the formation of plasmids in Streptomyces, their replication as extrachromosomal elements, and the interbacterial transfer of genetic information from Streptomyces. The specific aims are: (1) to further elucidate functions that govern integration/excision of the plasmidogenic element SLP1 of S. coelicolor, (2) to identify the genes and products involved in the replication of linear plasmids in Streptomyces, and (3) to understand the mechanisms by which cis-acting loci interact functionally and physically with plasmid-encoded and cell-encoded products to accomplish gene transfer from Streptomyces. The work will use a combination of genetic and biochemical approaches, including mutagenesis, gene cloning, and purification of proteins and other cell components. Together the investigations proposed are intended to address several key aspects of the evolution and spread of antibiotic resistance, and also to answer fundamental questions about the biology of extrachromosomal elements in the medically and biologically important genus, Streptomyces.